EPA study explains link between smog, heart problems

Story by

Bernice Yeung

Smog has been linked to heart problems and even death, and new research by the U.S. Environmental Protection Agency begins to explain why.

Researchers found that healthy young adults who have been exposed to ozone – which is a major component of smog – experience physiological changes that could be linked to heart ailments in vulnerable populations, such as elderly people with cardiovascular disease. Additionally, the study “provides a plausible explanation for the link between acute ozone exposure and death," lead author Robert B. Devlin said in a statement.

The study has special implications for Californians, who are exposed tosome of the highest ozone levels in the country.

Of the 10 regions in the country with the most ozone pollution, nine are in California, with Los Angeles-Long Beach-Riverside topping the list, according to the American Lung Association.

“Our ozone problem is the result of the combination of population, climate, terrain and industry,” with car exhaust as the main source of the pollutant in California, Dimitri Stanich, a spokesman for the California Air Resources Board, wrote in an email. “California has historically had the worst air pollution in the union. In the 1940s, there were smog events in the L.A. area where residents couldn’t see a city block.”

Ozone is created when pollutants from cars, power plants and other sources interact with sunlight.

To address ozone pollution, the air resources board requires car manufacturers to meet more stringent emission standards and regulates some chemical-based consumer products that may contribute to ozone during evaporation.

In its new study, EPA researchers exposed 23 healthy young adults to two-hour sessions of both clean air and ozone-polluted air at levels about two times greater than what residents in China or Mexico experience during the middle of the day. After exposure to the pollutant, the study subjects saw an increase in various cardiovascular indicators that could result in heart problems in people with heart disease, including vascular inflammation and a reduced ability to dissolve artery-blocking blood clots.

Though studies of ozone and human health abound, the new EPA study, published in the American Heart Association journal Circulation, is among the first to use human volunteers to explain how ozone can potentially kill people by causing heart attacks. Previous epidemiological studies have shown a connection using statistical analyses.

“It’s the strongest evidence that there is a true causal connection” between ozone exposure and heart health, and confirms and expands what has been suggested in previous studies, said Douglas Dockery, an environmental epidemiology professor at Harvard’s School of Public Health.

Health experts said that the latest EPA study is an important contribution to determining the extent of the relationship between ozone exposure and cardiovascular problems – an issue that is far from scientifically settled.

A larger, 90-person study among the elderly was recently launched by the Boston-based Health Effects Institute in conjunction with UC San Francisco and two other universities.

“There is not a universal set of studies that say, ‘Yeah, ozone definitely contributes to cardiovascular effects,' " said Dan Greenbaum of the Health Effects Institute. "But that may be because we have not looked at it the right way, and that is what we are trying to do with this study (of the elderly).”